Chest radiography represents some 40-50 percent of a radiology department's activity and currently suffers from some technical limitations. The large differences in penetration of the chest will cause a proper lung field exposure to underexpose the mediastinum. A large volume of lung tissue is imaged suboptimally due to dense overlying structures of the heart, diaphragm, and spine. Equalization techniques that use specially designed filters to preferentially attenuate the incident x-ray beam over the lung field and produce a more uniformly exposed image prove to be clinically impractical due to the difficulty of designing a good filter to match all patient builds as well as long set up time required for their use. We are proposing a specialized scanning imaging system that will optimally expose all areas of the chest film by measuring the beam attenuation for each point over the patient with an air ionization chamber that will automatically adjust the tube output to compensate for large changes in patient attenuation. We feel this image will allow good lesion detectability over the entire lung volume as well as in the mediastinum at doses that may be 1/2 of those currently used. We propose testing the impact of this unit with lung phantom studies and a small clinical trial.